I use Fidelity for an investment. Their website says I have a cost basis of $5000.00 invested in FUSVX. Now the balance of this mutual fund (which I believe is simply market value at closing from the previous day) reads 4947.77.

I also have a money market balance of 400 valued at 400. They take the .65% mutual fund return and add the 0% return for the money market and give me a .72% positive total return...?

I called Fidelity and talked to two representatives who could not give me a clear explanation of why this is. Basically, they said "it has to do with time and dollar cost averaging". I understand DCA; this feels like voodoo.

I have a TD ameritrade acct and their cost and gain/loss numbers make sense. Can someone explain Fidelity's seemingly magic number system?

Fidelity Definitions

Balance

The market value of each investment in your account as of the date displayed in the Returns As Of column.

Cost Basis

Generally, the total cash value of all your share purchases of a given investment option, accumulated based upon the original cash amount used to purchase shares, exclusive of any change in the price of a given investment over time. This basis is inclusive of all your share purchase activity, regardless of the type of activity (includes standard cash flows, such as contributions, exchanges and withdrawals, as well as non-cash flows such as interest, dividends and adjustments). Keep in mind that cost basis calculations are done at the investment option level. Due to gain/losses realized at the time of an exchange from one investment to another, adding up your cost basis for each investment option will not give you an account level cost basis
If your investments were transferred from another recordkeeper to Fidelity, your cost basis starts at the point your new shares were purchased here at Fidelity, except for stock funds. For company stock funds, your tax cost basis is transferred and thus reflected in cost basis number indicated in the table.

YTD

Your cumulative return of each investment since the beginning of the current year. Refer to the "Returns As Of" date to determine when this value was last calculated.

Ah, so if they are calculating the fund's return and not my return that makes sense!! I bought into the fund in April of this year. Though, clearly their representatives should KNOW THIS. And their definition should say "the funds return and not your return"
– P.Brian.MackeyAug 20 '15 at 13:30

Yes, you'll need to calculate your own return. I tend to use the XIRR function in an Excel spreadsheet: dates and totals of investments (cost) vs dates and totals of returns (including the current stock price on the date of calculation). Most investment websites I use tend to be very bad at showing what my current annualized return is, so I do it myself.
– Peter K.Aug 20 '15 at 13:32

Note here that YTD return is 2.32%. Fidelity says 0.65% so I'm not sure that's what they are doing either :\. The value in Fidelity is 73.50 and current as of 8/19/2015. So the chart you posted should match their YTD if that is the case.
– P.Brian.MackeyAug 20 '15 at 13:34

You'll notice the large dip immediately after the December 31st data point I've highlighted above. They may be calculating from January 1st, which is possibly much lower than the December number.
– Peter K.Aug 20 '15 at 13:36